I am mostly Wild player,and Krul the Unshackled is very good in Renolock deck,many times he deliver me a win jumping in play with cards like Doomguard and Voidlord :) So i like it so much,even crafted Golden version :) So those who like Reno style deck definitely should craft Krul.

A little trivia fact: Krul is technically the most powerful creature according to Lore in Hearthstone to date. He's not a simple demon that made it's way into the Kabal, rather an incredibly powerful Voidlord that is capable of destroying entire planets. Although even more powerful Void Gods exist (like Entropius), Kruul can easily devour and destroy characters like Ysera, Ragnaros, Y'shaarj, etc.

Surprisingly useful legendary. You can always add some demons to your hand with Kazakus Potion. And there are situations when you prefer to see Lord Jaraxxus as a 3/15 minion (play around burst damage, Sacrificial Pact etc).

Krul is that much more fun in Wild, alongside Mal'Ganis. If you have a Doomguard in hand as well when you play Krul, you get a 9/11, 9/7, and 7/9 Charge for 9 mana, and become Immune. That's a fairly strong turn. xD